Cleaning stations are used in electrophotocopiers to remove residual toner particles from the surface of a photoconductive drum each time a copy is made. Typically, as shown in U.S. Pat. No. 4,259,003, these cleaning stations include a conductive cleaning roller engaging the surface and rotating in the opposite direction and a conductive wiper blade. The roller and blade are supplied with biasing potentials to assist in the removal of the charged toner particles from the image-bearing photoconductive surface. The removed particles are flushed away by cleaning liquid, which is directed into a trough created between the roller and the wiper blade.
It is preferable to form the wiper blade from material which is highly compliant, thus allowing the tip of the blade to maintain contact with the drum surface without excessive pressure. The blade material must also be conductive and capable of maintaining its conductivity in the presence of the cleaning liquid. In addition, it is preferable to form the blade of material which is inherently conductive as opposed to materials which are impregnated with carbon to render them conductive, as impregnation results in highly conductive hot spots which may be detrimental to the photoconductive surface. Furthermore, the conductivity is affected by the cleaning liquid which usually is a liquid developer. However, the bulk conductivity of inherently conductive, unimpregnated, compliant materials suitable for wiper blades is relatively low.
In cleaning stations of the prior art, the entire wiper blade is formed of inherently conductive material; and its electrical resistance is relatively high. Furthermore, when the tip of the blade becomes worn, the entire wiper blade must be replaced.